The ideological divisions gripping the Democratic Party intensified as rivals rounded on frontrunner Joe Biden over health care, immigration and race during the second presidential debate.
Former vice president Mr Biden was repeatedly forced to defend his decades-old political record against pointed attacks from his younger rivals, who charged that his eight-year relationship with President Barack Obama was not reason enough to earn the Democratic nomination.
The attacks on Mr Biden in the second presidential debate were most vivid coming from Kamala Harris, who declared his willingness to work with segregationists in the US Senate during the 1970s could have had dramatic consequences on the surge of minority candidates in political office.
She added that it could have prevented her and fellow presidential candidate Cory Booker, both of whom are black, from becoming senators.
“Had those segregationists had their way, I would not be a member of the United States Senate, Cory Booker would not be a member of the United States Senate, and Barack Obama would not have been in a position to nominate Mr Biden to become vice president,” she said.
Mr Biden clearly anticipated a tough night and told Ms Harris: “Go easy on me, kid,” as they greeted one another on stage before the debate began in Detroit.
The dynamic showcased the challenges ahead for Mr Biden and his party as Democrats seek to rebuild the young and multiracial coalition that helped Mr Obama win two presidential elections.
Those differences were debated on a broad menu of issues including health care, immigration and women’s reproductive rights.
But it was the discussion of race that marked an escalating rift shaping the Democratic primary.
At the same time, polls show Mr Biden has far more support from minority voters than his challengers, especially in the crucial early voting state of South Carolina.
Mr Booker, who at times adopted the position of peacemaker, also took Mr Biden to task over criminal justice issues and his role in passing a crime bill while a Delaware senator in the 1990s.
When Mr Biden fought back by criticising Mr Booker’s tenure as mayor of Newark, New Jersey, before becoming a New Jersey senator, Mr Booker shot back: “You’re dipping into the Kool-Aid and you don’t even know the flavour.”
For Democrats, the internal fight, while common to almost every primary cycle, is one many would rather avoid, favouring instead a focus on defeating Mr Trump.
Several candidates said they thought Mr Trump should be impeached and others called him a racist.
“The first thing I am going to do is Clorox the Oval Office,” Kirsten Gillibrand said.
For the first time in the months-old Democratic contest, Ms Harris faced pointed attacks on her plan to provide universal health care.
She faced criticism from all sides this week after releasing a competing plan that envisions a role for private insurance with strict government rules, but she wants to transition to a single-payer government-backed system within 10 years.
There were also tense exchanges on immigration that pitted Mr Biden against former Obama housing secretary Julian Castro, the only Latino candidate in the race.
While the first primary votes are six months away, there is a sense of urgency for the lower-tier candidates to break out.
More than half the field could be blocked from the next round of debate if they fail to reach new polling and fundraising thresholds implemented by the Democratic National Committee.